This invention relates to a mobile communication system and in particular, to the method of multiplexing channels in the mobile communication system.
It is well known in the art that CDMA technology gives us its greater bandwidth efficiency and multiple access capabilities than FDMA or the TDMA technologies. Generally, in CDMA communication system, signal spectrums to be transmitted are spread with codes assigned to respective users, and then, are multiplexed. When receiving the transmitted signal as a reception signal, each of the users despreads the reception signal with the code assigned to each user to extract data signal relating to each user. Thus, the codes for spreading signal spectrums serve to identify each user in the CDMA communication system and to define channels. If the codes are composed of eight and sixteen bits, it is possible to define code pattern of 256 and 65536, respectively. The number of code patterns allows the system to have high multiple access capabilities. Besides, the high Capabilities are accomplished on one frequency carrier wave, so that the system can gain high efficiency of bandwidth.
Recently, mobile communication systems tend to be used by a great number of users. Development of CDMA technology accelerates the increase of the number of users more and more. In order to respond to the increase of the users, a lot of code patterns have been required. On the other hand, the code patterns are finite in number and, in addition, all of the code patterns can not be always assigned to users. Under the circumstances, the code patterns might be exhausted with the increased users in the future, and emergence of high efficient system is expected in the art.
This invention therefore improves the CDMA communication system to provide new communication system having much greater multiple access capabilities.
According to one aspect of the present invention,. a mobile communication system employs the following method to assign a channel to a specific one of mobile terminals existing on a service area provided by a base station which has a plurality of codes. Herein, the mobile terminal is referred to as the MT, and also, the base station is referred to as the BS.
In one aspect of the present invention, the plurality of the codes are classified into a plurality of channel groups (also referred to as xe2x80x9cterminal groupsxe2x80x9d), so that a plurality of group codes of the channel groups are allocated to the plurality of the codes, respectively. One of the channel groups to which the specific MT belongs is determined, and a unique address identifier in the channel group is labeled for the specific MT. The group code allows to distinguish between the channel groups, while the address identifier allows to distinguish one of the MTs from the other MTs in each channel group. That is, a combination of the address identifier and the group code is unique in the service area which the BS provides. Therefore, the specific MT is defined, as the channel, the combination of the address identifier labeled for the specific MT and the group code corresponding to the channel group to which the specific MT belongs.
The channel assigning method may be executed for the MT moving into the service area of the BS and may be uniformly executed for all of the MTs existing on the service area of the BS. In this case, the BS may notify the MTs of the respective combinations of the address identifiers and the group codes.